A federal lab confirmed that an outbreak of severe respiratory illness among children in Colorado is an uncommon virus that at first causes symptoms similar to the common cold but can quickly worsen.

Children’s Hospital of Colorado said Monday that samples sent last week to the Centers for Disease Control and Prevention tested positive for enterovirus 68.

Area hospitals are reporting a surge in children with severe respiratory illnesses, and Children’s has seen a sharp upswing in the past few days.

At least two other states also have confirmed outbreaks. There are no known fatalities, according to CDC.

Children’s has treated 447 respiratory cases in its emergency departments around Denver and admitted 39 to the hospital since Thursday. Last week, Children’s reported it had treated more than 900 children since Aug. 18 and admitted 86.

Enterovirus 68 is an uncommon strain of a common family of viruses that typically hit from summertime through autumn. The virus typically causes illness lasting about a week, and most children recover with no lasting problems. In some cases, however, more severe symptoms develop.

Children’s has treated newborns to 21-year-olds, said Dr. Christine Nyquist, a pediatric infectious disease physician. Both emergency room visits and admissions were up 12 percent to 15 percent over the same time last year.

National Jewish Health on Monday also reported a “significant surge” in urgent-care visits and hospital admissions because of children whose respiratory infections had worsened their asthma.

Rocky Mountain Hospital for Children reported seeing five to seven times the normal caseload of respiratory infections for early September.

Matthew York, 12, stayed home from school Friday because of mild cold symptoms, said his father, Ben York, of Northglenn.

“At 1 a.m. Saturday morning, he came into our room and said, ‘Mom, Dad, I can’t breathe.’ He was hunched over and struggling for every little breath.”

At Rocky Mountain, Matthew quickly improved with continuous oxygen, York said, but he was still in the pediatric intensive-care unit Monday evening. Hospital staff told Ben York that, if the family had waited another hour, the infection could have been lethal.

Dr. Tracy Butler, medical director of the pediatric intensive-care unit at Rocky Mountain, where the outbreak began over Labor Day weekend, said many children’s cases turn around in 24 hours, but some children have been on a ventilator for a week.

She expects, judging from reports in other states, that the outbreak will last about a month. She advises parents with asthmatic children to start their asthma-control medications to keep inflammation at a minimum before they contract the virus.

For Melissa Lewis’ 9-year-old son, Jayden Broadway, a runny nose, slight cough and small appetite after school Friday night turned to alarm by Saturday, with Jayden struggling to breathe.

Repeated nebulizer treatments with his asthma medicine — every two hours — didn’t ease his breathing, she said. His pediatrician told the family to go to the hospital as a precaution. They went to Children’s Hospital at 6 p.m. for treatment, but he had to be admitted at midnight.

“I was shocked he had to be admitted,” Lewis said. “It’s mind-blowing the way this happened. It’s so rapid. A little runny nose, a slight cough.”

And then he couldn’t breathe.

“It’s the worst thing to see your child not be able to breathe,” Lewis said. “He was having a hard time. It was so labored.”

The blanket over his chest would slowly rise with his effort, she said, and then just collapse.

With help breathing, Jayden is fighting off the virus and might be able to go home Tuesday.

“He’s a trooper,” Lewis said. “He’s been doing excellent.”

Jayden said some things about being in the hospital were “kinda cool,” but he was missing his sister, 7-year-old Jada, who couldn’t visit because the hospital has prohibited visits by children under age 13.

Cases also have been confirmed in Missouri and Illinois. In Kansas City, Mo., nearly 500 children have been treated at Children’s Mercy, and some required intensive care, according to authorities.

At Children’s Hospital of Colorado, 19 of the 25 samples sent to CDC tested positive for enterovirus 68.

A CDC spokesman said the agency also is testing to see if the virus caused respiratory illnesses reported in children in Alabama, Georgia, Iowa, Kansas, Kentucky, Ohio, Oklahoma and Utah.

Dr. Mary Anne Jackson, director of infectious diseases at Children’s Mercy, said local cases began appearing in mid-August and they appear to have peaked in her area.

Dr. Anne Schuchat of the CDC said the strain involved also appeared in the United States last year and in specimens from other countries. She said the CDC learned it had reappeared in this country last month when authorities in Chicago and Kansas City notified the agency about severe illnesses in children who had to be hospitalized.

Jayden’s grandmother, Joan Lewis, said it had worried her to see her scooter-pushing, soccer-loving grandson snub favorites like chicken and noodles and pancakes and head to his bedroom Friday after school.

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